The peer reviewed literature and patents disclose numerous examples of defined structures prepared by templating methods. In each of these examples a variety of defined structures have been employed to create an imprint upon a substrate prior to removal of the templating agent. An important feature of such templates is the facility by which they may be removed. Typically, templates are removed by degradation of the material of the template. For example, polystyrene microspheres that form defined pores in a membrane or monolithic ceramics and glasses may be readily removed by thermal treatment of the substrate material to decompose the microspheres. In addition to solid templates, foaming agents have been introduced into materials to afford pores created from entrapped bubbles.
There are numerous drawbacks to these conventional techniques. For example, subjecting the substrate or matrix to significant changes in temperature, pressure, and/or relatively aggressive chemical environments in order to decompose templates often results undesirable changes to the characteristics of the substrate/matrix material. Additionally, such removals and use of foaming agents often result in relatively non-uniform void structures. Still further, the substrate/matrix may retain residues from the template that alter the function or physical characteristics of the substrate. For example, template removal rarely allows for the substrate/matrix to maintain chemical functionality within the inner surface of the substrate vacated by the template. In addition, template defined materials are often prepared using expensive templates or labor intensive multi-step procedures that limit final applications to high value-added products and have precluded widespread industrial use. In fact, the use of templates has been so costly and/or burdensome that many defined structural materials are manufactured using self-assembly of substrate materials that define and commonly determine the final structure of the material (e.g., synthetic zeolites).
In view of the foregoing, a need exists for an adaptable and versatile method for preparing well-defined, cost-effective template prepared materials.